ldr to adc

No you can not connect an RTD not an LDR directly to a microcontroller pin. These two sensors are mere temperature dependemt resitors; meaning that the value of their resistance varies with temperature. You need to convert this variable resistance to a voltage so that it can be sensed with an ADC. The best strategy is to supply them with a constant current (from a current source) and measure the developed voltage. Feed this voltage to the ADC to convert to digital form.

Re: LDR and RTD to ADC of microcontroller

try connecting it using the inbuilt ADC pins (Eg: PORTA for ATmega16),choose appropriate mux channel and program d algorithm using AVRSTUDIO GCC compiler,output digital signals can be taken from other ports.Watch out videos of tishitu electronics on youtube.

Re: LDR and RTD to ADC of microcontroller

A Simple arrangement to use these sensors with an ADC is to form a voltage divider circuit. This can be done very easily by connecting the LDR in series with a fixed resistor. Since the two resistors (fixed resistor and LDR) are forming a voltage divider circuit there will be a certain voltage drop across each resistor.
As the resistance of the LDR varies with the intensity of the incident light there the voltage drop across it will also vary.
This change of voltage can be sensed by any ADC wheather it is a built in ADC inside a controller or an independent ADC.
The circuit diagram of a simple circuit that explains the above arrangement is added an an attachment.